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Lecture outline. History/Introduction Microbiological Techniques/ Diversity Diversity/ Structure and function Prokaryotic structure and function Nuclear structure, cell walls etc…. Prokaryotic structure and function Prokaryotic structure and function Bacterial growth.

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lecture outline
Lecture outline

History/Introduction

Microbiological Techniques/ Diversity

Diversity/ Structure and function

Prokaryotic structure and function

Nuclear structure, cell walls etc….

Prokaryotic structure and function

Prokaryotic structure and function

Bacterial growth.

Bacterial Genetic systems (LK)

simplified bacterial cell

Cell-membrane

Plasmid

Flagellum

Capsule

Cell-wall

Fimbrae

Nucleus

Simplified Bacterial Cell
cell surface structures and cell walls
Cell Surface structures and Cell walls

A. Flagellae

B Pili and fimbrae

C. Capsules

D. Cell Walls, membranes and Peptidoglycan

Membrane structure and function

Gram Positive. Teichoic acids

Gram negative. Outer membrane/ Lipopolysaccharide

cell surface structures and cell walls1
Cell Surface structures and Cell walls

A. Bacterial flagellae

Helical. Several times the length of the cell

Single polar - E.coli as shown

two polar - Pseudomonas spp. Very motile

Axial filaments. Spirochetes.

Subunits of flagellin protein.

Helix arrangement. Self assembly.

At least 12 genes control the basal components in E.coli.

cell surface structures and cell walls cont
Cell Surface structures and Cell walls cont…

Mechanism of motility

Rotate rigidly, motor in cell membrane

ATP not hydrolysed. Involves proton motive force in respiring membrane

Multiple flagellae rotate in bundles

Polystyrene beads

Cell

(Berg.H C. 1973)

slide6

Bacterial flagellum structure and mechanism

Flagellum rotates via

“motor” in active

membrane

Gram Positive

Gram Negative

cell surface structures and cell walls cont1
Cell Surface structures and Cell walls cont…

Chemotaxis

Motile bacteria swim toward attractants

Positive and negative chemotaxis

Sense environment. Surface receptors

CHEMORECEPTORS

over 20 recognised in E.coli

Glucose

Random motion

cell surface structures and cell walls cont2
Cell Surface structures and Cell walls cont…

B. Pili and fimbrae.

Filamentous appendages up to 30 m long and 20-30nm thick

Self assembly

Adhesion to surfaces

Sex pili involved in conjugation

C.Capsules and slime

External layer of polysaccharide (except B antracisD-glutamic acid polymer)

C/N nutrition dependent

Homo or hetero polysaccharide (usually amino hexoses)

Serves to protect cells egphagocytosis, dessication etc.

d cell walls membranes and peptidoglycan
D. Cell Walls, membranes and Peptidoglycan

Membrane defines INSIDE and OUTSIDE

Cell wall constructed OUTSIDE

Wall is a RIGID structure. PEPTIDOGLYCAN

Various polymers are interlinked to make ONE big polymer.

Serves to protect the cells from harsh environments

TEICHOIC ACIDS found only in GRAM positive cells

either glycerol phosphate polymer

or ribitol phosphate polymer

membrane structure and function
Membrane structure and function

Cytoplasmic or Plasma membrane

Glycerophospholipids; fatty acid esters of glycerol 3-phosphate

Arranged in fluid bilayer

Many proteins arranged in membrane

substrate transport functions

respiration

secretion and cell wall growth enzymes

Glycerol 3-phosphate

HYDROPHYLIC

Long chain fatty acid

HYDROPHOBIC

gram positive and gram negative cell types

Peptidoglycan

Lipopolysaccharide

Teichoic acids

1-2nm

20-80nm

Peptidoglycan

Cell membrane

Cell membrane

Gram Positive and Gram Negative Cell Types

Outer-membrane

GRAM POSITIVE

GRAM NEGATIVE

slide17

[NAM-NAG] n

L

D

L- NH2

D

[D]

Peptidoglycanstructure